1. Technical Field
The invention relates to phase-locked loops (PLL's) and more particularly to compensating for variances in tuning voltage of a voltage-controlled oscillator (VCO) of a PLL during deactivated times of the PLL.
2. Background of the Invention
Portable telephones, such as cellular telephones, are very popular and becoming more popular and widespread every day. People enjoy the convenience of having a phone at their disposal no matter where they are. Impinging upon this convenience is the need to recharge the battery of the telephone periodically. If this time between recharges can be made longer, then the telephone becomes more convenient and useful.
To reduce battery power consumption, portable telephones sometimes are made to have an operating state called a paging mode. In this mode, the phone periodically turns on the phone's receiver to check whether there is an incoming call. The phone is only on (activated) for a short period of time, and off (deactivated) for times between the on times, thus saving total average current and improving standby time (i.e., time when the phone is not in use).